ISO 6139:1993 Preview
Aluminium ores -- Experimental determination of the heterogeneity of distribution of a lot
This standard was last reviewed and confirmed in 2008. Therefore this version remains current.
The heterogeneity of distribution is characterized by the distribution variance and is determined by experimentally measuring the sampling variance. Because both the composition variance and distribution variance contribute to the measured sampling variance, it is necessary to separate these two components. Two methods of data analysis are permitted: Visman's theory of sampling which uses classical statistics and the variogram method which gives a better estimate because of taking into account serial correlation between adjacent increments.